Measuring gauge and method of making the same



Aug. 1944- J y A. J. MITCHELL 2,355,007 I MEASURING-GAUGE AND METHOD OF MAKING THE SAME Filed June '19, 1943 Patented Auntie man, STATES.

-- T orrics assseer masunmo canon asn more or MAKING and sans Abraham .1. Mitchell, Stratford, 0cm, alsignol' to Mitchell-Bradford Chemical Company, Bridgeport,0onn.,afirm Application June 19, ms, Serial No. use

2 Claims. (01. ss-ics) mechanic. The usual gauge-surfaces are hardened steel finished to proper gauging size and finish. After a gi -eater or iess length of time, depending upon the amount of use of a gauge,

the gauging-surfaces wear so as to bring about lack of, a proper degree of trueness and lack of a proper degree of dimensional size, or of distance between two compiemental gauge-surfaces, H which is not readily detectable by the eye, and

therefore it is necessary for a skilled mechanic to periodically take each of the gauges used in a manufacturing plant using them, and subject them to careful time-consuming tests to determine whether or not the inaccuracy-condition of 7 any of the gauge-surfaces is sufficient to require the re-correction oi the gauge or the discarding,

of the same. A

I have discovered that by treating the hardened finished steel gauge-surfaces with an queous liquid chemical treatment which will change the iron of the gauge-surface to black iron oxide, this treatment does not add any additional thickness of surface upon the finished steel gauge-surface, but rather that it chemically changes the iron of the surface down to a predeterminable depth to the black oxide of iron, so that in the final flnished condition, no position or dimension of the gauge-surface, or distance between gauge-surfaces, is changed. Thus it will be seen that in accordance with my invention, the gauge-surfaces can be hardened and finished to final proper gauging size and finish without making any allowance whatever for the final forming .of the iron oxide surface, since this does not superimpose any additional depth on topof the steel gauge-surface, but instead, chemically forms itself as; a black oxide which extends from the position of the original finished steel gauge-surface downward to a predetermined depth of a small fraction of one-thousandth of one inch. Thus itwillbeseenthat as the angels used and as areas-of the black-oxide surface, are worn down to the underlying metallic iron or bright steel s face. the underlying brightsteel surface-portime are exposed,andowingtothe contrastin color or optical appearance between the thusexposed steel areas and the adjacent not-womthrough black-oxide areas, the worn-through areas are immediately visible on inspection, thus acting as a tell-tale indication of the worn or inaccuracy-condition in the gauge-surface, and the number of these worn-through areas and their total area thus optically indicates the degree of the worn or inaccuracy-condtion of the gauge-surface.

One object of this invention, therefore, is to provide an improved measuring-gauge having one or more mainly-met'aliicflmn hardened-steel gauge surface-parts each of which has first been hardened and finished to form one or more mainly-metallic-iron and hardened-steel gaugesurfaces'oi proper gauging size and finish, and then has been treated by an aqueous liquid chemical which changes the metallic iron of the gaugesurface to black oxide without changing any position or dimension of the gauge-surface. so that the gauge can be manufactured and have its gauge-surfaces finished true and to size before the black oxide or colored surface is formed thereon without having to make any allowance for the addition oi the black-oxide surface.

Another object of this invention is to provide an improved method of making the foregoing described measuring-gauge.

with the above and other objects in view. as will appear to those skilled inthe art from the present disclosure, this invention includes all features in the said disclosure which are novel over the prior art. 1

In the description and claims, the various parts and steps are identified by specific terms for convenience, but they are intended to be as generic in their application as the prior art will permit. In the accom it drawing forming part of the present disclosure, in which two different gauges are shown with the present invention applied thereto:

"Fig. i is a front elevation of a gauge made in I accordance with the present invention;

Fig. 2 is a face view in the direction of arrow A of Fig. 1, illustrating a face view of one of the the black-oxide gauge-surfaces thereon.

Referringto 1"1gs.'1 to s of the drawing, the gauge is which is one forms! a "go, no-go" gauge, includes a body ii carrying the two opposed omplemented goigauge surface-parts l2 and the two opposed complemental no-go" gauge surface-parts it, the form of which is well known to those skilled in the art..

The gauge surface-parts l2 and it are formed of hardenable tool steel and after they have been hardened and ground, lapped and polished to form proper truly-flat, parallel gauging-surfaces with proper space between each pair of complemental surfaces, the gauge has been ready for use prior to my invention, with the defect or drawback, however, that wear of any of the gaugesuri'aces' out of true and/or out of proper diaasaoo'r six to eight pounds of the combined salts referred to together with aboutthree quarts of water, will result in about one gallon of solution having a boiling point within the range stated.

Another suitable coloring or black-oxide-forming solution can be made by having an aqueous solution of the proper strength tor the desired boiling point, by employing solids consisting of 85% sodium hydroxide, sodium nitrate and 5% sodium nitrite.

Normally, a few minutes will generally secure a good depth of coloring, and this coloring will be substantially of uniform depth or penetration throughout the surface treated.

Inasmuch as the temperature of treatment is in the neighborhood of only about 300 F., it is below any temperature which would-substantially draw the temper of the hardened steel gaugemensional spacing to one another is not detectable by the eye, but must be found by a careful test by a mechanic especially skilled in carrying out such testing of gauges. V

In makingthe gauge in accordance with my invention, however, I take the gauge NI in its iinishedsizeandformlustasillustratedinl igl but without any black oxide having been formed on the black-indicated areas as yet, and Ithen treat it in an aqueouschemical bath at a moderwhich will produce the black-oxide areas without substantially. reducing the hardness of the hard ened carbon tool steel gauge surface-parts i2 and i3 and without chang n any position or dimenate temperature in the neighborhood of 300 F. Y

surfaces. Therefore, the providing of the black surface leaves a hard under surface which supports the'black oxide so that, in addition to thelow friction resistance and high wear resistance of the black-oxide surface, the black-oxide surface will stand considerable mechanical abuse without 'When the black oxide is newly formed, it is uni formly black all over as indicated on Fig.2. But I after the gauge has been used some time so that the gauge-surface is subjected to sliding over the parts to be measured, there is a wearing action which takes place with the result-that gradually sion of a gauge-surface or position of one of'them relatively to another. so that after the blackoxide gauge-surfaces are formed, the distance between the ccmplemental gauge-surfaces is just the same as it was before the black-oxide-forming treatment. I I

In carrying out this black-oxide-forming treatment, the entire gauge can be immersed in the chemical bath in which instance all exposed ironcontaining surfaces would be changed into blackironoxide. so that where, as is usual, the entire gauge shown in Pig. 1 has surfaces which are mainly metallic iron, the entire gauge would be black after removal from the black-oxide-forming bath. 0r instead of blocking all the surfaces of-- shown in Fig. 2, formed into the black oxide, but

in order to make sure that the entire gaugesuri'ace and its boundary edge is changed to black oxide, it is easier to have the black oxide extend back at least a short distance beyond the gauge-surface as illustrated in .Fig. 1.

One suitable coloring or black-oxide-forming bath or solution can, be made by taking 90% sodium, hydroxide, 5% potassium nitrate and 5% sodium nitrate and adding them to suflicient water to give a convenient consistency and preferably in relationship to the water content which will result in the bath having c/boiling point substantially between 280 l". and 320.F. From 7 mall areas II at various locations on the gaugesurface will be [worn through to the underlying metallic steel surface which will thereby he exposed and present a sharp color contrast with the, surrounding black area to thus warn anyone inspecting the gauge that the, gauge-surface is starting to wear. After still further use, still greater areas llwillappearandtheremaining black portion of the area will become more scatt'ered and of less totaiarea as time goes alongso that, as schematically indicated in Fig. 4,- the gauge-surface area has worn .down still more.

face has been worn still more and thus acting as an automatic visual telltale indication of the degree of inaccuracy-condition of the gauge-surface. Also, if a black'gauge-surface were tampered with, as for example by illing, grinding or bumng, such tampering. or the result of the tampering, would be immediately visible. After thegauge-surfaces have been worn to such an extent as may in any given instance be considered the limitof tolerance, the gauge or gauge-parts are corrected in any of the well-known suitable ways or are discarded and replaced by a new gauge or game-parts. I

Fig. 6 illustrates a diiferent form of go, no-go gauge Ill which has acylindrical "go" gaugesurface It and a cylindrical "no-go-gauge -surface H at opposite ends of the gauge. The Bill'- faces l8 and II are formed with the black-oxide surface as hereinbefore described. gAnd as the black oxide wears through, it will disclose that fact by gradually uncovering more and greater areas of underlying steel surface of contrastlns color appearancerto the acent black-oxide areas, all as hereinbefore more fully described in connection with Figs. 1 to 5 inclusive.

While the black oxide coa an oil, grease, wax or other suitable material thereto which is absorbed by the black-oxide coating and which decreases the frictional resistance of the surface and therefore increases the wear resistance. Also, while the black-oxide surface has resistance to rusting, the oil or other impregnating treatment also further increases the resistance to rusting. I

One important characteristic of my invention is that the black-oxide surface can be formed at below 350 F. which is important in order that the gauge-surfaces may have substantially the maximum steel hardness that can be given to them, since if the, gauge-surfaces were to be subjected to temperatures high enough to substan-;

tially soften or draw the temper or hardness of the steel below the high hardness originally given tothe gauge-surface prior to the black-oxideforming treatment, such softening would increase the coefficient of friction and increase the wear on the surface, thus causing it to more readily M 'Ket out of true.

The invention may be carried out in other specific ways than those herein set forth without departing from the spiritand essential characteristics of the invention, and the present emor treatment has 7 a low coefilcient of friction and a high resistance to wear, it also is porous, and permits of applying face parts of proper gauging size and finish, and each of which said gauge-surface parts has one or more black oxidized gauge-surfaces, each black-oxidized gauge-surface being characterized by low-friction resistance and high-wear resistance in gauging operations and of a substantlally-uniform depth of a fraction ofone-thousandth of an inch throughout the black-oxidized gauge-surface,whereby when one or more portions of the black-oxidized gauge-surface is worn of! 'and exposes the underlying mainly-metalliciron surface, the marked difierence in optical appearance between the thus-exposed mainlymetallic-iron surface-portions and the adjacent black-oxidized surface-portions provides a visual tell-tale indication of the inaccuracy-condition of the gauge-surface.

2. The method of preparing one or more gaugesurfaces of a measuring-gauge having one or more mainly-metallic-iron hardened-steel gaugesurface parts which have been processed to proper gauging size and finish, comprising: treating each gauge-surface at below 350 F. by an aqueous liquid chemical material which oxidizes the metaliic iron of the gauge-surface to black iron oxide, each black iron oxide gauge-surface being characterized by low-friction resistance and bodiments are, therefore, to he considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

I claim:

1. A measuring-gauge having one or more mainly-metalliciron hardened-steel gauge-suras J. MITCHELL. 

